Lapidaryforum.net
Let's Rock => Rockhounding Tips, Maps, Trips Etc. => Topic started by: lithicbeads on August 27, 2015, 07:45:18 PM
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We have had this creek picked out for about six weeks but when we were here last the humidity was about 10% and the temps were in the mid 90's , perfect fire weather. We could not find a place to park where the trucks catalytic converter was not touching dry grass so we decided to come back later. A low is coming in from the ocean so the humidity was up to about 50% and I brought and old fashioned weed whip to cut the grass.One arm for the crutch and one for the weed whip got the job done.
I had found a piece of jade in the creek in the few minutes we were there last time so I had high expectations. The creek is very steep with many chest high water falls to be negotiated.After surmounting the first one we found huge amounts of blueschist which was very exciting. Blueschist is formed when undersea basalt is subducted and experiences an odd metamorphism. Blueschist facies metamorphism means that the rock was subjected to very high pressures , 7,000 to 9,000 times air pressure at sea level in this case but with temperatures not exceeding 400 degrees C. Since pressure is virtually instantaneous we have to assume there are conditions where temperature is not at the depth required for the relevant pressure . Rock is a good insulator , excellent really, and a wedge of rock can go down in the subduction trench and only have the interior get to 400C if it goes down very fast and emerges very fast as well. We are talking about 26 kilometers ( a kilometer is about 6 tenths of a mile) to get to the required pressure. Why is blueschist exciting? It is often very beautiful , blue and chatoyant , but it is too soft for lapidary purposes. It is however associated very strongly with jadeite and it has been found in a few places within ten miles of this creek.
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Very little chert in the creek so my buddy did not get distracted by the blue cherts ( uncuttable for various reasons) and we focused on the large selection of serpentines which ranged from white to powder blue and bright mottled green . Best serp selection I have ever seen but a big sledge is necessary to break them as they were very large. I found jades and I think one was the best of the year. It is not pictured as we had to rush out so my friend could make an engagement back home but I will be cutting them tomorrow.The biggest I left there because it was mostly buried and weighed in excess of 200 lbs.That is packlithic country.This creek floods horrendously during the snowmelt and the woods are full of alternate stream beds and big multiton boulders. This is good for us oldsters because it will be completely turned over exposing new rocks each summer. The creek is red from iron. The bedrock is iron formation an undersea iron with just a little silica. These are very common here and are made adjacent to the undersea black smokers out at the plate edge .
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My buddy is posing in front of a big red cedar that has diverted the creek.
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On the upstream side of the cedar the debris is piled about 5 feet high which was enough to stop these two granite boulders.
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Here is a view on the way out.
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We looked a bit more then I found this schistose piece of jade and we decided to have lunch. Yes Helene it was smoked salmon.
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I have not seen iridescence from iron eating bacteria since I was a kid. The area I grew up in was full of iron mines and bog iron was still being formed by bacteria as it is here. Bog iron gets big , in the multi ton range. We hit a vertical wall of debris and decided to call it a day as we had 15 miles of bone jarring white knuckle driving before we hit pavement. Helene got to experience the white knuckle part on a nearby mountain when we were driven off the road by a skidding dump truck . A one lane twisty steep road is not a good place to speed with a loaded ten ton dump truck but that seems to be the game as I have been forced into the ditch before in another place by a speeding dump truck. In that case the other option was to steer in the other direction and fall 1500 feet down the clearcut mountain.We will be back.
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Gorgeous!
I haven't seen water that red from Iron before. I would think there must be a large ore deposit upstream someplace.
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The bedrock here is all iron .The bedrock is never more than a few hundred feet down buried in glacial till. All the rock in the pictures areglacial till and as we went up slope the bed rock was very close to the surface as we could see an iron cliff a few hundred yards away.
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Great pictures and great geology lesson...as always. Thanks for taking us on yet another adventure.
:icon_salut:
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Beautiful country! It is common for us to have above 90 with below 10% RH but that is expected of us. The webs between your toes must be in awful condition with conditions like that. The use of a weed whip reminds me of college in the mid sixties and clearing weeds off of an earthen dam, hot sticky work in Oklahoma. The fire from catalytic converters reminds of a large grass fire at an event at Arcosanti near Cordes Junction here in Arizona, the event holders just had folks parks their cars in an unworked grass field and the converter set the grass ablaze and burned a few dozen cars. It is something most folks just don't think about.
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You find the most interesting, beautiful locations for your adventures. Is this on national forest land? The iridescence is very interesting. You mentioned bog iron; I've found chunks of rust-colored oxidized, faintly iridescent, very heavy layered stone on the peninsula before, not (apparently) magnetic, though not tested with anything particularly powerful. Is bog iron a term that could be applied to stone like that?
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Yes this is national forest land . A thousand acre clear cut is just uphill. They left the old growth as a way to protect the road from washing out , a strategy that has worked well. The old growth corridor is a contour of the slope and it extends about 400 yards down the slope with the road in the middle of the contour.Yes what you found sounds like bog iron but bog iron has various densities .
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You are an amazing dude Frank. I do not know how you do it with your legs. The beauty of the places and the rocks must give you the will to never give up.
OR, you just love to entertain us to the max. hahaha
Jim
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Stupidity with a big dose of go until you die is the key. Getting out is much more important than finding at my age.Of course I have to give this all up for a 3 week trip to Wyoming , staying at Old Faithful and visiting friends.